Examinando por Autor "Costantin, L."

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Acceso Abierto
A few StePS forward in unveiling the complexity of galaxy evolution: light-weighted stellar ages of intermediate-redshift galaxies with WEAVE
(EDP Sciences, 2019-11-21) Costantin, L.; Lovino, A.; Zibetti, S.; Longhetti, M.; Gallazzi, A.; Mercurio, A.; Lonoce, I.; Balcells, M.; Bolzonella, M.; Busarello, G.; Dalton, G.; Ferré Mateu, A.; García Benito, R.; Gargiulo, A.; Haines, C.; Jin, S.; La Barbera, F.; McGee, S.; Merluzzi, P.; Morelli, L.; Murphy, D. N. A.; Peralta de Arriba, L.; Pizzella, A.; Poggianti, B. M.; Pozzetti, L.; Sánchez Blázquez, P.; Talia, M.; Tortora, C.; Trager, S. C.; Vazdekis, A.; Vergani, D.; Vulcani, B.; Istituto Nazionale di Astrofisica (INAF); Comunidad de Madrid; Fundación Caixa; Agencia Estatal de Investigación (AEI); Vulcani, B. [0000-0003-0980-1499]; De Arribas, L. P. [0000-0002-3084-084X]; Zibetti, S. [0000-0003-1734-8356]; Talia, M. [0000-0003-4352-2063]; Tortora, C. [0000-0001-7958-6531]; Pizzella, A. [0000-0001-9585-417X]; Ferré Mateu, A. [0000-0002-6411-220X]; McGee, S. [0000-0003-3255-3139]; Gargiulo, A. [0000-0002-3351-1216]; Longhetti, M. [0000-0002-6142-4822]; Gallazzi, A. [0000-0002-9656-1800]; Vergani, D. [0000-0003-0898-2216]; Haines, C. [0000-0002-8814-8960]; Costantin, L. [0000-0001-6820-0015]; Pozzetti, L. [0000-0001-7085-0412]; Dalton, G. [0000-0002-3031-2588]; Iovino, A. [0000-0001-6958-0304]; Sánchez Blázquez, P. [0000-0003-0651-0098]; Merluzzi, P. [0000-0003-3966-2397]; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. The upcoming new generation of optical spectrographs on four-meter-class telescopes, with their huge multiplexing capabilities, excellent spectral resolution, and unprecedented wavelength coverage, will provide invaluable information for reconstructing the history of star formation in individual galaxies up to redshifts of about 0.7. Aims. We aim at defining simple but robust and meaningful physical parameters that can be used to trace the coexistence of widely diverse stellar components: younger stellar populations superimposed on the bulk of older ones. Methods. We produced spectra of galaxies closely mimicking data from the forthcoming Stellar Populations at intermediate redshifts Survey (StePS), a survey that uses the WEAVE spectrograph on the William Herschel Telescope. First, we assessed our ability to reliably measure both ultraviolet and optical spectral indices in galaxies of different spectral types for typically expected signal-to-noise ratios. We then analyzed such mock spectra with a Bayesian approach, deriving the probability density function of r- and u-band light-weighted ages as well as of their difference. Results. We find that the ultraviolet indices significantly narrow the uncertainties in estimating the r- and u-band light-weighted ages and their difference in individual galaxies. These diagnostics, robustly retrievable for large galaxy samples even when observed at moderate signal-to-noise ratios, allow us to identify secondary episodes of star formation up to an age of ∼0.1 Gyr for stellar populations older than ∼1.5 Gyr, pushing up to an age of ∼1 Gyr for stellar populations older than ∼5 Gyr. Conclusions. The difference between r-band and u-band light-weighted ages is shown to be a powerful diagnostic to characterize and constrain extended star-formation histories and the presence of young stellar populations on top of older ones. This parameter can be used to explore the interplay between different galaxy star-formation histories and physical parameters such as galaxy mass, size, morphology, and environment.
Acceso Abierto
Dynamical Structure of Small Bulges Reveals Their Early Formation in ΛCDM Paradigm
(The Institute of Physics (IOP), 2020-01-17) Costantin, L.; Méndez Abreu, J.; Corsini, E. M.; Morelli, L.; De Lorenzo Cáceres, A.; Pagotto, I.; Cuomo, V.; Aguerri, J. A. L.; Rubino, M.; Comunidad de Madrid; Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR); 0000-0001-6820-0015; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The Λ cold dark matter (ΛCDM) paradigm of galaxy formation predicts that dense spheroidal stellar structures invariably grow at early cosmic time. These primordial spheroids evolve toward a virialized dynamical status as they finally become today's elliptical galaxies and large bulges at the center of disk galaxies. However, observations reveal that small bulges in spiral galaxies are common in the nearby universe. The prevailing belief that all small bulges form at later times from internal processes occurring in the disk represents a challenge for the ΛCDM scenario. Notably, the coevolution of bulges and central supermassive black holes (SMBHs) at early phases of galaxy evolution is also at stake. However, observations have so far not provided conclusive evidence against their possible early origin. Here, we report new observations of small bulges showing that they follow the mass–velocity dispersion relation expected for virialized systems. Contrary to previous claims, small bulges bridge the gap between massive ellipticals and globular clusters. This dynamical picture supports a scenario where systems over seven orders of magnitude in stellar mass form at early cosmic time. These results alleviate the tension between ΛCDM simulations and observations at galactic scales. We hypothesize that these small bulges are actually the low-mass descendants of compact objects observed at high redshift, also known as red nuggets, which are consistently produced in cosmological ΛCDM simulations. Therefore, this also suggests that the established coevolution of SMBHs and large bulges naturally extends to spheroids in the low-mass regime.